Bracket-like structural member

ABSTRACT

An improved bracket-like structural member designed to improve structures where a rigid space frame can fulfill a structural purpose. An exemplary structural member comprises two straight tubes that each comprise a graphite fiber wrapped foam cylinder, and a curved tube that comprises a graphite fiber wrapped foam arc segment whose distal ends abut an end of each straight tube. Graphite fiber cloth overlaps interfaces between the curved tubes and the straight tube. A strut interconnects adjacent ends of the straight tubes. The present invention is readily applicable to more than two elements terminating at a joint.

BACKGROUND

[0001] The present invention relates generally to structural members, and more particularly, to an improved bracket-like structural member for use as a rigid space frame.

[0002] Historically, space frames were built-using brackets that were fabricated separately from the space frame. These brackets are expensive and are heavy. Joints using prefabricated joint brackets have failed under testing.

[0003] It is therefore an objective of the present invention to provide for an improved bracket-like structural member for use as a rigid space frame.

SUMMARY OF THE INVENTION

[0004] The present invention provides for a bracket-like structural member designed to improve satellite antenna towers and other structures where a rigid space frame can fulfill a structural purpose. The present invention has reduced mass, enhanced stiffness and strength compared with prefabricated joint brackets. The present invention causes space frames to have reduced mass and greater stiffness and strength characteristics compared to space frames incorporating prefabricated brackets. Thus, space frames become a practical structural alternative to solid panel construction. This allows for more accessibility to satellite components during fabrication and assembly. The present invention provides a manufacturing approach to space frames that may be used repeatedly, while allowing for flexibility in choosing structural dimensions and geometry.

[0005] An exemplary structural member comprises two straight tubes that each comprise a graphite fiber wrapped foam cylinder, and a curved tube that comprises a graphite fiber wrapped foam arc segment whose distal ends abut an end of each straight tube. Graphite fiber cloth overlaps interfaces between the curved tubes and the straight tube. A strut interconnects adjacent ends of the straight tubes.

[0006] The strut of the bracket-like structural member, referred to as a “bracketless” bracket, reinforces a joint comprising the graphite fiber wrapped foam cylinder and arc reinforced by the overlapping graphite fiber cloth. This eliminates the need for a heavier gusset plate. Additionally, the strut changes the manner in which loads are transferred through the joint. Thus radial or tensile cracking stresses that traditionally cause delamination are either eliminated or significantly reduced using the present invention.

[0007] The present invention is readily applicable to more than two elements terminating at a joint. For example, a strut disposed at 45° may be coupled between additional pairs of tubes, in the same manner as the first two tubes. The present invention may also be used to create frame connections in three dimensions, i.e., space frames.

[0008] The present invention employs laminate and structural analysis software to design space frames employing the bracket-like structural member or bracketless brackets. The resulting space frames are lighter, less expensive and more reliable than previously available space frames. The present invention allow for fabrication of space frames that are lighter and have stronger joints than similar previously designed structures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The various features and advantages of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawing, wherein the sole drawing figures illustrates an exemplary bracket-like structural member in accordance with the principles of the present invention.

DETAILED DESCRIPTION

[0010] Referring to the sole drawing figure, it illustrates an exemplary bracket-like structural member 10 or “bracketless” bracket structure 10 in accordance with the principles of the present invention. The exemplary bracket-like structural member 10 is formed using a master tool. An exemplary master tool may be provided by a block of foam routed out with channels to accommodate graphite fiber wrapped foam cylinders 11 a, 11 b and a graphite fiber wrapped foam arc segment 12 interconnecting the fiber wrapped foam cylinders 11 a, 11 b.

[0011] More specifically, an exemplary bracket-like structural member 10 comprises two straight tubes 11 a, 11 b and one curved tube 12 that are formed around a foam cylinder 15 and foam arc segment 16. The straight and curved tubes 11 a, 11 b, 12 comprise graphite fiber wrapped foam members. The two straight tubes 11 a, 11 b are joined to the curved tube 12 at a joint. Graphite fiber cloth 14 is wrapped in an overlapping manner at interfaces between the straight tubes 11 a, 11 b and the curved tube 12. A strut 13 reinforces the joint and interconnects ends of the straight tubes 11 a, 11 b. The strut 13 connects to the straight tubes 11 a, 11 b a short distance away from abutting ends of the straight and curved tubes 11 a, 11 b, 12.

[0012] The foam arc segment 12 is preferably smaller in diameter than the foam cylinders 11 a, 11 b. The arc segment 12 is wrapped with more layers than the foam tubes 11 a, 11 b. The outside diameter of the straight and curved tubes 11 a, 11 b, 12 is substantially identical.

[0013] The strut 13 may be formed in a number or ways. The strut 13 may be formed as tightly rolled graphite fiber cloth. The strut 13 may be formed by routing an appropriately angled channel in the master tool. The strut 13 may be formed by wrapping cloth around the straight tubes 11 a, 11 b, and sewing fibers to connect the tubes 11 a, 11 b and the strut 13 together.

[0014] Thus, improved bracket-like structural members have been disclosed. It is to be understood that the above-described embodiments are merely illustrative of some of the many specific embodiments that represent applications of the principles of the present invention. Clearly, numerous and other arrangements can be readily devised by those skilled in the art without departing from the scope of the invention. 

What is claimed is:
 1. A structural member comprising: two first tubes that each comprise a graphite fiber wrapped foam cylinder; a curved tube that comprises a graphite fiber wrapped foam arc segment whose distal ends abut an end of each first tube; graphite fiber cloth overlapping interfaces between the first tubes and the curved tube; and a strut interconnecting the first tubes near their adjacent ends.
 2. The structural member recited in claim 1 wherein the foam arc segment has a cross section that is smaller in diameter than the diameter of the foam cylinder.
 3. The structural member recited in claim 1 wherein the arc segment is wrapped with more layers of graphite fiber than the first tubes.
 4. The structural member recited in claim 1 wherein the outside diameter of the graphite fiber wrapped first and curved tubes is substantially identical.
 5. The structural member recited in claim 1 wherein the strut comprises tightly rolled graphite fiber cloth.
 6. The structural member recited in claim 1 wherein the strut comprises cloth wrapped around the first tubes and fibers that sew the first tubes and the strut together.
 7. A structural member comprising: two or more first tubes that each comprise a graphite fiber wrapped foam cylinder; two or more curved tubes that each comprise a graphite fiber wrapped foam arc segment whose distal ends abut an end of a selected pair of the two or more first tubes; graphite fiber cloth overlapping interfaces between each selected pair of the first tubes and the respective abutting curved tube; and two or more struts interconnecting each selected pair of first tubes near their adjacent ends.
 8. The structural member recited in claim 7 wherein the foam arc segment has a cross section that is smaller in diameter than the diameter of the foam cylinder.
 9. The structural member recited in claim 7 wherein the arc segment is wrapped with more layers of graphite fiber than the first tubes.
 10. The structural member recited in claim 7 wherein the outside diameter of the graphite fiber wrapped first and curved tubes is substantially identical.
 11. The structural member recited in claim 7 wherein each of the two or more struts comprise tightly rolled graphite fiber cloth.
 12. The structural member recited in claim 7 wherein each of the two or more struts comprise cloth wrapped around the selected pair of first tubes and fibers that sew the selected pair of first tubes and respective ones of the two or more struts together. 